In the past many schemes have been tried to accomplish the linear translation of rotary head devices along a guide. Such attempts have included the use of chain or cable drives powered by hydraulic cylinders, hydraulic motors, air motors, and the like. These systems have utilized and depended upon the integrity of chains and cables for operation and suffered their attendant, and high cost of maintenance.
In the case of a cable or chain failure, the rotary head mounted for vertical movement on a tower could descend rapidly, thereby creating the possibility of serious injury. Several direct coupled hydraulic cylinders schemes have been tried including the use of piggy-backed hydraulic cylinders. All of these attempts in the past have required the use of traveling hydraulic hoses which are subject to damage and/or severally restricted the available travel.